Linux Basics (6)

Linux Basics (vi)

Three loops and function knowledge points in shell scripts

First, the process control if structure

1. Simple If instance:

#!/bin/bashVar='/ETC/INIT.D'#var= '/DEV/SDA 'if[ -d $var] then echo"$var is directory"elif[ -b $var] then echo"$var is block"elif[ -F $var] then echo"$var is regular file"ElseEcho'Unknow'fi

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Execution effect:

2. Passing parameters to a script

eg

#3.shEcho $0echo $1echo $2echo $3Echo ${11}echo'$$'$ $echo'$*'$*Echo'[email protected]'[Email Protected]echo'$#'$#Echo'$?'$?

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Test results:

[[Email protected] ~] #  ./3.sh 1 2 3 4 5 6 7 8 9./3. SH1238755$* 1 2 3 4 5 6 7 8 91 2 3 4 5 6 7 8 9$#  ten$? 0

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Two. While of the cyclic structure

while (condition)

Do
Action
Done

When an infinite loop is required we choose the while:
Write a script to let the user input, enter the number through, output error re-enter

#!/bin/bashlogin=0 while[$login! = 1]do Read-P'Please input your name:'name Read-P'Please input your password:'pwdif[$name = ='Egon'] && [$PWD = ='123'] then echo'Login sucessful'Login=1Fidone

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Run and view results:

[[Email protected] ~] # ./4.sh  123login Sucessful[[email protected] Gandong]#

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Third, the circular structure for

Shell format for

 for inch {1..10}doecho $idone

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[[Email protected] ~] #  12345678910

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An example of applying a loop and conditional judgment write:

Vim 6. SH while:d o Read-P'Please input your name:'name Read-P'Please input your password:'PSDif[-Z $name] | | [-z $PSD] ThenContinuefiif[$name ='Alex'-A $psd ='alex3714'] then echo'login successful, welcome da SB'             while: Do read-P'Please input your cmd:'cmdif[$cmd ='quit'] Then Breakfi $cmd doneElseEcho'Username or password is error'Fidone Echo'========================================================'~

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Four, the function knowledge point

Functions in the interactive shell

eg

Vim 7'aaa'bbbb';} ABC

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Operation Result:

[[Email protected] ~] # Vim 7.sh [[Email protected] ~] # ./7.sh aaabbbb

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Linux Basics (6)